JPH06317730A - High-density multifiber optical cable - Google Patents

Abstract

PURPOSE:To provide a high-density multifiber optical cable which particularly lessens the generation of propagation loss by a laminated structure of coated optical fiber ribbons as the high-density multifiber optical cable formed by laminating and assembling the plural coated optical fiber ribbons in a prescribed housing space. CONSTITUTION:This high-density multifiber optical cable is the optical cable having the structure laminated and assembled with plural sheets of the coated optical fiber ribbons 11 in the long-sized ribbon housing space part 12 and is formed by interposing a dummy ribbon DT on the uppermost layer side and/or lowermost layer side of the laminated and assembled coated optical fiber ribbons 11. The concentration of the stresses on the coated optical fiber ribbons 11 is averted by the stress relieving effect of the dummy ribbon DT, by which good transmission characteristics are assured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-density multi-fiber optical cable in which a plurality of optical fiber tapes are laminated and assembled in a predetermined storage space portion, and particularly, a transmission loss due to a tape laminated structure is small The present invention relates to a high density optical fiber cable.

[0002]

2. Description of the Related Art In recent years, an optical cable having a structure as shown in FIGS. 5 and 6, for example, has been proposed as a high-density multi-fiber optical cable. In the optical cable C _{1 of} FIG. 5, a plurality of optical fiber tapes 1 are put in a groove 2 having a long groove structure to be stacked and assembled, and the groove 2 is twisted around the outer periphery of the tension member 3 at the center. In the case of the optical cable C ₂ of FIG. 6, the sheath 4 is coated on the outside, and in the case of the optical cable C _2, a slot groove forming a long groove structure provided in the longitudinal direction of the slot 5 through which the tension member 3 is passed. A plurality of optical fiber tapes 1 are put in 5a to be stacked and assembled, and the sheath 4 is also coated on the outer side thereof.

In a cable having a structure in which a plurality of optical fiber tapes are stacked and stored in such a predetermined storage space portion, the number of optical fiber tapes can be easily increased or decreased as needed, and therefore the optical fiber tapes can be easily increased or decreased. The structure is extremely advantageous for high-density mounting.

[0004]

However, in the case of the cable structure as described above, the linear expansion such as when the cable is bent like when the cable is wound around the drum or when the cable is exposed to a low temperature condition. When the influence of the difference in the ratio is large, the meandering phenomenon is likely to occur as shown in FIG.
The optical fiber tape 1 located on the uppermost layer or the lowermost layer is a bottom surface of the tape housing space portion, the sheath 4 portion (or a restraining tape portion when a restraining tape or the like is provided inside the sheath 4), etc. Part of the tape is strongly pressed onto the optical fiber tape, and the top or bottom optical fiber tape 1
However, there is a problem in that the transmission characteristics of are extremely deteriorated.

In particular, in recent years, there is a tendency to thin the fiber coating layer (to reduce the diameter of the wire) in order to further increase the density (in order to increase the degree of integration). In such a case, there is a problem that the deterioration of the transmission characteristics of the optical fiber tape 1 located on the uppermost layer or the lowermost layer is further increased.

The present invention has been made in view of such a conventional situation, and at least the optical fiber tapes on the uppermost layer side and the lowermost layer side, which are in contact with the outer member, concentrate stresses from the outer member. It is an object of the present invention to provide a high-density multi-fiber optical cable in which the problems of receiving and transmitting characteristics are less likely to occur.

[0007]

According to the present invention, there is provided an optical cable having a structure in which a plurality of optical fiber tapes are stacked and assembled in a long tape storage space portion. There is a high-density multi-fiber optical cable characterized in that a dummy tape is interposed on the uppermost layer side and / or the lowermost layer side of the fiber tape, and if necessary, the dummy tape has high water absorption performance. It is on the optical fiber cable.

[0008]

In the present invention, since the dummy tape is interposed between the outermost member and the optical fiber tape on the uppermost layer side or the lowermost layer side which comes into contact with the outer member as described above, the cable is placed on the drum. When the cable is bent or exposed to a low temperature condition like winding, the optical fiber tape becomes meandering, and the optical fiber tape on the uppermost layer side or the lowermost layer side is locally stress-concentrated. Also in this case, since the dummy tape relieves the stress, good transmission characteristics are secured. Further, when a dummy tape having a water absorbing property is used, even if moisture enters the tape storage space for some reason, deterioration due to the moisture can be effectively prevented, which is excellent for a long period of time. Excellent transmission characteristics can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a high density multi-fiber optical cable according to the present invention. In this high-density multi-fiber optical cable C ₁₁ , 11 is an optical fiber tape, 12 is a rectangular groove that forms a long tape storage space portion made of polyethylene or various engineering plastics, 13 is a tension member, and 14 is a sheath. In this optical cable C ₁₁ , among the plurality of optical fiber tapes 11 stacked and assembled in the square groove 12, the dummy tape D having a stress relaxation action is provided on the uppermost layer side and the lowermost layer side portion.
_T is interposed.

As the dummy tape D _T , for example, a tape made of a single material such as nylon, PBT, polyethylene, PET, PC, non-woven fabric, or a laminated tape obtained by combining a plurality of these tapes can be used. Further, as the dummy tape D _T having a water absorbing property, the above-mentioned nylon, PBT, polyethylene, PET, P
C, a dummy tape made of a composite material such as a non-woven fabric or the like, which is provided with a water-absorbing function by applying a water-absorbing paint or a water-absorbing powder on one or both sides, or the tape itself is formed of a water-absorbing material It may be one.

As a concrete method of stress relaxation with the dummy tape D _T , (1) a method of using a tape having a Young's modulus of about 1 to 10 kg / mm ² which is excellent in cushioning property and utilizing the cushioning property (2) A method of using a tape having a bending rigidity that is substantially the same as that of the optical fiber tape 11 (for example, Young's modulus = about 100 to 200 kg / mm ² ). When utilizing the protection function provided by the tapes, the tapes may be provided with appropriate lubricity.

In the dummy tape D _T in the case of the above (1), for example, as shown in FIG.
Even during meandering, the dummy tape D _T is accommodated without following the meandering of the optical fiber tape 11, and the optical fiber tape 11 on the uppermost layer side and the sheath 14 (when there is a restraining tape inside the sheath 14). The stress is concentrated on the side of the optical fiber tape 11 due to the soft cushioning action because it is present (present) between the optical fiber tape 11 on the lowermost layer side and the bottom surface of the corner groove 12 on the lowermost layer side. This can be effectively prevented.
That is, an excellent effect of relaxing stress concentration can be obtained. Also,
When the dummy tape D _T having a water absorbing property is used, the dummy tape D _T itself absorbs the water that has entered the tape storage space and removes the water from the space. The adverse effect of water on the fiber tape 11 can be prevented, and a good waterproof function can be obtained.

Further, the dummy tape D having a bending rigidity almost the same as that of the optical fiber tape 11 in the case of the above (2).
_{At T} , the result is apparently equivalent to the case where another optical fiber tape 11 is placed outside the optical fiber tapes 11 on the uppermost layer side and the lowermost layer side, so that, for example, as shown in FIG. When the optical fiber tape 11 meanders, the dummy tape D _T meanders following the meandering of the optical fiber tape 11. Therefore, the stress is concentrated on the dummy tape D _T , and the optical fiber tapes 11 on the uppermost layer side and the lowermost layer side are protected from the stress concentration by the dummy tape D _T. That is, an excellent effect of relaxing stress concentration can be obtained. Also in this case, the dummy tape D _T having water absorption property
When using, the same good waterproof function as described above can be obtained.

FIG. 4 shows another embodiment of the high-density multi-core optical cable according to the present invention. In this optical cable C ₁₂ , the long tape accommodating space portion is the slot groove 15 a of the slot 15. Is the optical cable C ₁₁ shown in FIG.
A dummy tape D _T having a stress relaxation effect is interposed between the uppermost layer side and the lowermost layer side of the plurality of optical fiber tapes 11 that are also laminated and assembled in the slot groove 15a. . Therefore, this optical cable C
_{Also in 12} , similar to the optical cable C _{11 in} FIG. 1, an excellent effect of relaxing stress concentration can be obtained.

Incidentally, the groove type high-density multi-core optical cable shown in FIG. 1 (the optical fiber tape used has a thickness of 180 μm).
(12 strands, tape thickness 0.02 mm, tape width 2.3 mm), when using a soft dummy tape, it is a hard dummy tape that has almost the same bending rigidity as an optical fiber tape. The transmission loss after the cable was formed was measured for each of the case of using No. 1 and the case of using no dummy tape, and the results shown in Table 1 were obtained. Here, for the measurement of the transmission loss after making the cable, after making the cable, an OTDR (optical pulse tester) is used to measure the measurement wavelength λ.
Was performed in two ways, for 1.3 μm and for 1.55 μm.

[0016]

[Table 1]

From Table 1, when the dummy tape is used, particularly when the harder dummy tape having almost the same bending rigidity as the optical fiber tape is used, the transmission loss is small and the excellent transmission characteristics are obtained. I understand that it will be done.
On the other hand, it can be seen that the transmission loss is considerably large and the stress is concentrated on the optical fiber tape without the dummy tape.

In the embodiment of FIG. 1 described above, the long tape storage space portion is a square groove, but the present invention is not limited to this, and the cross-sectional shape of the groove is a U-shaped U groove. In some cases. Further, the opening of the groove is not limited to the outward direction, but the opening may be twisted toward the tension member side. Further, the number of twisted steps (number of layers) of the groove is not limited to one. Further, in each of the above-described embodiments, as a preferable case, the dummy tape is interposed between the uppermost layer side and the lowermost layer side portion of the optical fiber tape 11, but in the present invention, although the stress relaxation effect is somewhat lowered, The dummy tape may be interposed in only one of them.

[0019]

As is apparent from the above description, the high-density multi-fiber optical cable according to the present invention has a structure in which a plurality of optical fiber tapes are stacked and assembled in a long tape storage space portion. Since it is an optical cable and a dummy tape is interposed on the uppermost layer side and / or the lowermost layer side of the laminated and assembled optical fiber tape, the cable is bent like when the cable is wound around a drum,
Or even when the optical fiber tape is meandering due to being exposed to low temperature conditions, and the optical fiber tape on the uppermost layer side or the lowermost layer side is locally stress-concentrated,
Due to the stress relaxation effect of the dummy tape, concentration of stress on the optical fiber tape can be avoided, and good transmission characteristics are secured. In addition, when a dummy tape having a water absorbing property is used, it is possible to effectively prevent the deterioration of the transmission characteristics due to the infiltration of moisture, so that the deterioration of the transmission characteristics is prevented even in an environment where water is easily infiltrated. Not stable characteristics are obtained.

[Brief description of drawings]

FIG. 1 is a schematic partial vertical sectional end view showing an embodiment of a high-density multi-core optical cable according to the present invention.

FIG. 2 is a schematic partial vertical cross-sectional side view when a soft-tapping dummy tape is used in the optical cable of FIG.

FIG. 3 is a schematic partial vertical sectional side view in the case where a stiff dummy tape is used in the optical cable of FIG.

FIG. 4 is a schematic partial vertical sectional end view showing another embodiment of the high-density multi-core optical cable according to the present invention.

FIG. 5 is a schematic vertical sectional end view showing an example of a conventional high-density multi-fiber optical cable.

FIG. 6 is a schematic vertical sectional end view showing another example of a conventional high-density multi-fiber optical cable.

FIG. 7 is a schematic partial vertical sectional side view showing a meandering state of an optical fiber tape in a conventional high-density multi-core optical cable.

[Explanation of symbols]

11 Optical Fiber Tape 12 Tape Storage Space (Groove) 13 Tension Member 14 Sheath 15 Slot 15a Tape Storage Space (Slot Groove) C _{11 to} C ₁₂ High Density Multi-Core Optical Cable _DT Dummy Tape

Front page continuation (72) Inventor Koichiro Watanabe 1440 Rokuzaki, Sakura-shi, Chiba Fujikura Co., Ltd.Sakura factory (72) Inventor Hiroyuki Sawano 1440 Rokuzaki, Sakura-shi, Chiba Fujikura Sakura factory (72) Invention Suehiro Miyamoto 1440 Rokuzaki, Sakura City, Chiba Prefecture Fujikura Ltd. Sakura Factory (72) Inventor Shigeru Tomita 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. An optical cable having a structure in which a plurality of optical fiber tapes are stacked and assembled in a long tape storage space portion, and the uppermost layer side and / or the lowermost layer of the stacked and assembled optical fiber tapes. A high-density multi-fiber optical cable with a dummy tape on the side. 2. The high-density multi-fiber optical cable according to claim 1, wherein the dummy tape has a water absorbing property.